CVE-2026-47774 (GCVE-0-2026-47774)

Vulnerability from cvelistv5 – Published: 2026-06-17 16:58 – Updated: 2026-06-30 12:10
VLAI
Title
Envoy vulnerable to HTTP/2 memory exhaustion via cookie header size bypass and HPACK amplification
Summary
Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. The issue arises from the combination of two behaviors. First, cookie header bytes are not fully accounted for during request header size validation in Envoy. Second, HPACK header block limits in oghttp2/quiche are enforced on encoded bytes without a corresponding limit on total decoded header size. Together, these behaviors allow a malicious client to cause large decoded header allocations while bypassing the intended request header size protections. Versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a fix. No complete workaround is known short of applying a fix. Possible temporary mitigations include disabling downstream HTTP/2 where operationally feasible; enforcing stricter request header and cookie limits before traffic reaches Envoy; and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-405 - Asymmetric Resource Consumption (Amplification)
  • CWE-770 - Allocation of Resources Without Limits or Throttling
  • CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)
Assigner
References
Impacted products
Vendor Product Version
envoyproxy envoy Affected: < 1.35.11
Affected: >= 1.36.0, < 1.36.7
Affected: >= 1.37.0, < 1.37.3
Affected: >= 1.38.0, < 1.38.1
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Red Hat Red Hat OpenShift Service Mesh 2.6     cpe:/a:redhat:service_mesh:2.6::el9
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Red Hat Red Hat OpenShift Service Mesh 3.0     cpe:/a:redhat:service_mesh:3.0::el9
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Red Hat Red Hat OpenShift Service Mesh 3.1     cpe:/a:redhat:service_mesh:3.1::el9
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Red Hat Red Hat OpenShift Service Mesh 3.2     cpe:/a:redhat:service_mesh:3.2::el9
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Red Hat Red Hat OpenShift Service Mesh 3.3     cpe:/a:redhat:service_mesh:3.3::el9
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}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.